https://www.youtube.com/watch?v=xnVgbdkK_Iw

1. Beverage Antennas
Presented by Matt VK2RQ
(based on material from Al Penney VO1NO / VE3 and Tom
Rauch W8JI)

2. 2
Why separate TX / RX antennas?
Because, they have different requirements:
●
TX antennas need to deliver strongest possible
signal into target area compared to other antennas.
●
Efficiency and gain are most important factors.
●
RX antennas need to have best Signal to Noise
Ratio (SNR) – gain and efficiency are not
necessary.

3. 3
Is Ant A better than Ant B?
Antenna A
Antenna B
(+3dB gain vs Antenna A)
Diagrams from ON4UN’s
Low Band DXing

4. 4
Is Ant A better than Ant B?
Single 720-foot Beverage.
Two 720-foot Beverages.
Spaced 70 feet apart.
Diagrams from ON4UN’s
Low Band DXing

5. 5
What do we gain?
●
Gain single Beverage: -11.2 dBi
●
Gain two Beverages (70-ft sp): -8.2 dBi
●
So, a pair of Beverages (with 70-ft spacing) has 3 dB gain
over a single Beverage.
●
But, has anything actually been gained in terms of
Signal/Noise ratio?

6. 6
Directivity vs Gain
NO – nothing has been gained!
●
The pattern is still practically identical
●
Front/Back is the same
●
Front/Side is within 0.47dB
●
Unwanted noise is external to the antenna. Because
the directivity of the two antenna systems is the same,
the Signal/Noise ratio is exactly the same for both.
●
We must use Directivity when comparing RX Antennas,
not gain.

7. 7
How much Gain do we need?
How much Negative Gain can we tolerate
with RX antennas?
●
Modern receivers are very sensitive.
●
If you can easily hear an increase in background noise
when switching from a dummy load to an RX antenna
under quietest conditions, then gain is sufficient.
●
Minus10 to minus 20 dBi Gain is generally fine for most
occasions.

8. 8
Noise
●
The sum of all unidentified signals (thunderstorms,
man-made, cosmic etc.).
●
Requires its own presentation!
●
RX antennas can reduce noise through:
−
Directivity
−
Null placement
−
Noise canceling devices
−
Height

9. 9
Basic Beverage Antenna

10. 10
Theory Of Operation
Diagram from Joseph Carr’s
Practical Antenna Handbook

11. 11
Influence of Length
Following slide shows EZNEC results for a Beverage
with following characteristics:
●
2 meters high
●
Over good ground
●
600 Ohm termination
●
0.55 to 4.4 wavelength
●
160 M band

12. 12
Radiation Patterns per Length
-4.0 dBi
4.4λ
-4.7 dBi
3.3λ
-6.3 dBi
2.2λ
-7.6 dBi
1.68λ
-9.9 dBi
1.1λ
-14.3 dBi
.55λ
Diagram from ON4UN’s
Low Band DXing

13. 13
Maximum effective length
free space
in wire
If free space wave gets
any further ahead, it will
start to cancel wave in wire

14. 14
How High?
●
Not as critical as many think
●
General rule:
– Higher Beverages produce higher output
– Higher Beverages have larger side-lobes
– Higher Beverages have a higher elevation angle
– Higher Beverages have a wider 3-dB forward lobe
●
Laying on ground to 6 meters high is acceptable
●
1.5 x Antler Height is good idea!
●
2.5 meters is a good compromise

15. 15
Supports
●
Metal, non-metallic – doesn’t
matter as long as antenna is
insulated
●
Poles, fence posts, trees, sheds,
misbehaving children – whatever
is available
●
Do not wrap wire around an
insulator
●
Try to keep it straight and level,
but minor variations are okay

16. 16
Supports

17. 17
Ground Quality
●
The better the ground, the lower the output
●
Ground quality has little impact on radiation angle
●
The poorer the ground, the less pronounced the nulls
between the different lobes
●
Directivity remains almost constant
●
Beverage does not work well over salt water

18. 18
Gain and Radiation Angle
Gain Curves
Radiation Angle Curve
Diagram from ON4UN’s
Low Band DXing

19. 19
Wire
●
Inefficient antenna anyway, so size not critical as long as
it is physically strong enough
●
Insulated, not insulated – doesn’t matter
●
Pre-stretch soft-drawn copper wire
●
Copper-clad and aluminum wire also okay

20. 20
Theoretical Surge Impedance
Z = 138 log4h
d
Where:
h = height of wire
d = wire diameter (in same units)

21. 21
Termination Resistor
●
Should be non-inductive
●
Antenna will pick up TX power and lightning surges, so use 2 watt resistor
●
Metal Film and Carbon Film cannot handle surges
●
Use Metal Ceramic or Carbon Composition
●
Use a Spark Gap
Photo from ON4UN’s
Low Band DXing

22. 22
Grounding
● One 8-foot ground rod may suffice
●
Will probably need two or more to stabilize the
ground system
●
Can supplement it with a number of short radials to
form capacitance hat to earth
●
On coax end of antenna, do not ground the coax
braid
●
Ensure the coax braid ground is no closer than 5
meters to the ground attached to the transformer

23. 23
One Beverage, Two Directions

24. 24
Basic Concepts
Common mode current vs Differential mode current
Kirchoff's Current Law
Transformer Action

25. 25
Use Common & Differential Mode
Radio signals arriving from the left induce
common mode current in the two wires
The transformer converts them to differential
mode current which travels back down the
Antenna to the receiver
Radio signals arriving from
the right simply induce
common mode current in the
two wires that heads down
the antenna. The transformer
plays no role for signals
coming from this direction.
Convert to differential
mode using an
auto-transformer

26. 26
Separating CM & DM currents
+V
0
-V
0
Common mode currents cancel in T4
primary winding, so nothing induced in
T4 secondary. Common mode currents
flow through T1 primary, induce a differential
mode current in T1 secondary, which is
available to a receiver connected to J1
Differential mode current in T4 primary
winding induces differential current in T4
secondary winding, which is available to a
receiver connected to J2.
Because antenna is a balanced line, centre
tap on T4 primary is at 0V ground potential,
so no current flows through T1 primary.

27. 27
Matching Transformers
Winding Binocular Cores
Pri Sec Pri Z Sec Z
Passes Passes Ohm Ohm
4 10 75 450
6 16 75 533
4 12 50 450
6 20 50 550
Note: Using Fair-Rite 2873000202
Type 73 Binocular Cores
(1 turn = 2 passes)
Diagram from ON4UN’s
Low Band DXing

28. 28
Reflection Transformer
●
Twist wire together for bifilar
winding
●
Bifilar winding for primary,
●
Single winding for secondary
through a binocular core
●
Join bifilar strands to form
centre tap and connect back
to secondary. Other side of
secondary goes to ground.
The remaining primary
winding goes to antenna

29. 29
Phasing Beverage Antennas
●
To improve directivity without using long antennas,
can phase individual Beverages
●
Two methods:
− Broadside
− End-Fire (or Staggered)
●
Each has its own advantages

30. 30
Broadside Phasing
●
Narrows frontal lobe
●
Front/Back remains the
same
●
Fed in phase
●
Multiband
●
Require wide spacing
●
0.5 λ spacing good
●
0.67 λ excellent!
To RX
Splitter
Coax
Coax
Beverage
Beverage
0.5 to 0.67 wavelength
RX Direction

31. 31
End-Fire Phasing
●
Greatly improves
Front/Back directivity
●
Front lobe remains
much the same
●
Spacing 5 meters
●
Stagger NMT 0.5 λ
●
20 m for 40 – 160m ant
●
30 m if only 80 – 160m

32. 32
Property too small?
● Try a BOG (Beverage On Ground)
– Termination ~ 200 to 300 Ohms
– Need a 4:1 matching transformer
– Use ferrite beads to decouple feedline
– May require a preamp
– Beverage’s first antennas were laid on the ground
Diagram from ON4UN’s
Low Band DXing

33. 33
For more information...
● The “Bible”!!
● Also check the website of
Tom Rauch, W8JI:
– http://www.w8ji.com
● Try the Topband Reflector
as well:
– http://lists.contesting.com/_t
opband/
● Joseph Carr’s book also
has lots of good stuff.